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mechanical wave Answered

I'm trying to build a tail of a fake animal, and the tail is kinda long (total length of about 3 feet), I have a 10 pound pull solenoid and I want the tail to kind of do a wave thing, like if you were do a wave with your arms ( not in a group, all by yourself where you hold your hands together, you know what I'm talking about). I know how to do the electronic part of it by sending pulses to the solenoid, but How would I convert that into a believable tail?

5 Replies

I keep thinking up all sorts of complicated mechanisms, but by far the easiest solution would be to make the tail very flexible side-to-side, and put some lead weights in the very tip. That way, you should be able to get at least a nice whip-like effect. You'll also need to rig a 5lb spring to pull back against your 10lb solenoid, so the tail behaves identical in both directions.
You should be able to get a much more natural movement with even just a single electrical motor. Doesn't need to be a servo - just pick one that is strong and silent enough for your purpose. Attach a wheel to the motor, and attach three or more cables around the circumference of the wheel. That way you can have multiple cables pulling out of phase on different parts of the tail, creating a wave-like motion.
You'll need to guide the cables so they don't interfere with each other - using standard servo gear (e.g. a servo horn for the wheel) might be most convenient - and you'll need something to pull against the cable - a spring or an opposing cable.

As I recall from my animatronics class, I think what you would do is make a sectioned tail with a servo motor at the base.
As long as you solenoid does not have a hard response to various voltages, i.e. if you can send different voltages to the solenoid and get different mechanical responses, you can make the motion realistic. You would need a sinusoidal oscillation chip or circuit driving the solenoid, though you'll probably have to tweak to the sine wave to account for the logarithmic distance properties of magnetic flux. Okay. Hope I wrote that clearly.
The solution

Oh I should have paid closer attention......um, Myth Busters recently created a "dolphin" and made it "as realistic as they could" to test if the presence of a dolphin would deter sharks (it certainly did seem to).
The tail was rather elaborate, but it was realistic.